(1) Field of the Invention
The present invention relates generally to connecting hydrophone elements in linear arrays, and more particularly to a means for connecting hydrophone elements to pass a sensing material, such as optical fiber, from one hydrophone element to another without adversely affecting the sensing material or measurement sensitivity.
(2) Description of the Prior Art
Hydrophone is a generic term describing a transducer that detects or monitors underwater sound. Hydrophones are typically pressure-actuated sensors and form the basis of sonar systems. Fiber-optic hydrophones employ fiber-optic cabling to sense pressure generated by acoustic wavefronts. Acoustic wavefront pressure produces measurable phase differences in the light waves guided by optical fiber.
A fiber-optic hydrophone typically includes a hollow, air-backed element known as a mandrel, with optical fiber wound on the mandrel surface. The advantages of multiple, smaller, interconnected elements when compared to a single larger element, are presented in U.S. Pat. No. 5,317,544, and such advantages include increased sensitivity and system robustness during deployment. Although prior art discusses the need to connect multiple mandrel-wound hydrophones in series with a single fiber, the interlink's design and material is often ignored. U.S. Pat. No. 5,317,544 mentions a means for compliantly connecting adjacent hydrophone components, while U.S. Pat. No. 5,475,216 claims a neoprene spacer, and U.S. Pat. No. 5,155,548 describes a spacer preferably formed of neoprene. Neoprene spacers or interlinks induce undesirable phase noise in the sensing fiber.
There is currently not a hydrophone interlink that allows a hydrophone array to pass through large bends across small diameter handling sheaves during array deployment, without placing excessive stress on the interlink or sensing fiber; and, there is not an interlink that additionally couples the sensing fiber to a structure such that the fiber is impervious to the structure's mechanical resonances.
What is needed is an interlink that is flexible during deployment, but during post-deployment (i.e., operation), ensures minimal fiber stretching from mechanical resonances of the interlink structure.